


I Think My Big Brother's New Roommate is Creepy, So I'm Going to Put an End to His Genocidal Plans!

by 8090200000



Category: Death Note & Related Fandoms, Death Note (Anime & Manga)
Genre: Alternate Universe - Canon Divergence, Canon-Typical Violence, Digital Art, Gen, Mixed Media, Sayu is determined to Ignore The Problem
Language: English
Status: In-Progress
Published: 2020-09-04
Updated: 2020-10-08
Packaged: 2021-03-07 00:21:45
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 2
Words: 4,343
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/26277829
Author URL: https://archiveofourown.org/users/8090200000/pseuds/8090200000
Summary: Despite the current battle between an all-powerful criminal killer and an enigmatic detective, Sayu Yagami is just your typical middle school girl. Until one day, her brother brought home… a demon!? It turns out, she’s the only one who can see it. Has Sayu gone mad? Nope, not on her watch. She’s determined to be a normal kid, even if that means hiding her newfound insanity from the world.
Comments: 10
Kudos: 37





	1. Me and Bobby and Bobby's Brother

**“Kyoko… I love you so much, what did I ever do to deserve this?” Shouto’s dazzling tears ran down his face. Kyoko was latched onto the arm of another, less dazzling man. She wanted to say something to Shouto, her face crumpled in defeat. This was clearly hurting her as much as it was hurting him. The silence between them interrupted by a serendipitous rainfall, as if the gods above were laughing at their cruel, cruel predicament. Finally, working up the courage to reach out to her lover and clear this misconception up once and for all, she spoke. “Shouto…! I--”**

“What the hell is going on here, even? Man, this stuff is really dumb.” The demon heckled, moving in front of the television to get a closer look at the show. 

“...” _Ignore it. It’ll move if you just ignore it._

“This is some seriously impressive technology here.” He poked at the screen. “And you people decided to use it for this? Really?” He didn’t move to look at her, as he knew he wasn’t getting an answer.

Concealing her irritation, Sayu stretched, adjusting her position on the couch subtly so she could see the screen again. _Alright, back to the show..._

 **\--“KYOKO!!!” Shouto screamed in anguish. “SHOUTO!!” Kyoko yelled back, equally anguished. She was hanging off of a building--** ****

_Wait, what? When did that happen!?_

**“HAHAHAH! Kyoko! If you can’t love me, then you will never love again!” The less-attractive guy that Kyoko was with a little bit ago declared. He pulled out a gun from his coat pocket, and was pointing it right at her--**

_HUH?! What!? What the hell is the point if she’s already in the process of falling to her death!?_

**The background music swelled into its famous ending theme… Signalling the end of the episode.**

_No! I didn’t even get to see what happe--_

**“Will Shouto save Kyoko? Will they make up? Will Horisawa finally follow his dreams of becoming the world’s greatest magician? Stay tuned for the next episode of** **_Loving Dreamers ~La Petit Ensemble~_ ** **Starring: Hideki Ryuga!”**

“...” _H.. Huh? What just happened? Why does Shouto need to save Kyoko? Who the hell is Horisawa!? How did I miss so much in that short period of time?_

“Heheheh, that was pretty funny. Can’t believe you watch this crap.” The demon said again, in that irritatingly lax voice of his.

“...” _Ignore it, Sayu._

He turned to look at me with those weird bulging eyes. “Haha, man, how are you and Light even related, let alone the same species? Humans are so strange.”

“...” **_Ignore it, it’ll go away._ **

“Oh wow, you look kinda mad. It’s almost like you heard me… Hey, you can’t see me, right?” It chuckled, as if there was some inside joke she wasn’t aware of. How _dare_ he? Just laugh it up. Like it hadn’t just ruined the one thing she’d been looking forward to the most this week!

“Grr…” Her annoyance swelling, she clenched the remote tightly. 

The demon had the audacity to look worried. “W-woah! Hold on there, kid! I didn’t mean to insult ya like that!” 

But… as much as she wanted to confront the bastard... 

“Gah!!” She got up and tossed the remote on the ground. “This sucks! Why doesn’t Kyoko just pick Shouto already! If I were her, I’d be all over any hunk played by Hideki Ryuga!!” She threw herself into the couch, and buried her face into the pillow. _There, now leave me alone._

She couldn’t see the demon anymore, but she heard it exhale a dramatic sigh of relief. “Phew, what the hell, don’t scare me like that.” It chuckled again, and she waited as that now familiar timbre hummed its way up the stairs.

“...Ugh..” Sayu tossed the couch pillow to the side. “Finally, it’s gone.” 

That thing just showed up one day about a month ago. It was a day she could never forget. After all, it was during the long-awaited premiere of _Loving Dreamers ~La Petit Ensemble~_...

- _Last month_ -

* * *

_“Hey, welcome home, Light!” Sayu said upon hearing the door opening. She didn’t bother turning to look, mom just left to buy groceries and dad won’t be home for a while, plus she’d just gotten comfortable on the couch, with a bag of potato chips in hand._

_Her brother sighed. “Sayu… shouldn’t you be studying right now?” Sounding equally exasperated and disappointed as any older brother would. “I heard from mom that your English grades have been slipping recently.” She could hear him taking his shoes off._

_Sayu did feel bad about that. She cringed inwardly thinking about what would have happened if it wasn’t Light that came home just then. Pouting, she threw her head back. “But Li-iiight! I’ve been waiting all year for this show to come out! It’s only an hour, after that I’ll go straight to my room to study, okay? Please don’t tell mom or dad!” With all the pre-pubescent gusto she could muster, she turned around to pout right at him. Even someone as responsible as her brother couldn’t resist her world famous puppy-dog pout--!_

_“Heh… sounds pretty important to her, Light. Maybe you should let this one slide.” Said the ominous devil-creature, standing idly behind her very human brother._

_She froze, pout still in place._

_Light’s lip twitched unnaturally before smirking playfully at her. “Alright, but you owe me one, Sayu.” He walked into the kitchen and grabbed the last apple from the fridge._

_Out of the corner of her vision, the creature’s eyes widened, and that gaping maw of his stretched further than she thought it could ever go. “Ooh, that looks delicious~! Too bad there aren’t any more… Hey Light, can’t you get more? This won’t be nearly enough!” It whined. It would have been endearing from a child, but from a giant, freakish ghoul of a thing, it was just kind of disturbing, really._

_“Y-eah! Thanks, bro! Just tell me when you need something!” She managed to get out. Sayu turned herself around and sat back on the couch._

_“...... Actually,” Light began. “There is something you can do.” He walked in front of the stairwell, at just the right angle for her to turn her head and look at him._

_“Do you think you can ask mom to buy more apples for me?” He asked nicely. “It must be these final exams getting to me, I’ve been craving them like mad.”_

_Sayu tensed… That was just a coincidence, right? “Sure, I mean, of course! But… why not just ask her yourself, Light?” It was such an innocent request, but all things considered, she couldn’t help but feel paranoid at the moment._

_Light chuckled shyly. “Well… It’s just that… You know how mom gets whenever I ask for things…”_

_She let out a breath she didn’t realize she’d been holding. Yeah, no, that made a lot of sense… The last time Light asked for something in earnest from their mother, it was during the end of elementary school. He wanted a tennis racket since he saw one on T.V., and the next thing he knew, he was enrolled in an after-school tennis club._

_In contrast, whenever Sayu asked for something, she got a 15 minute lecture about how spoiled she was, and then the next day she might find it on the counter. Emphasis on ‘might’._

_“...Alright, I’ll ask her. And don’t worry, I’ll be extra careful not to mention you, unless you want to become the leading expert on apple-ology.” Adding a playful wink at her brother._

_In her hysteria, she snorted at the thought of their mother signing him onto various apple related workshops and extra-curricular classes, and him as a professional apple scholar._

_Light apparently read her mind, and held up his apple as if to ponder it. “Well,” He added in a scholarly tone. “I must admit, the biological structure of the apple is quite fascinating… Perhaps the secrets of the universe are contained within its core.”_

_Silence, followed by genuine laughter shared between the siblings._

_Sayu pretended not to hear the waspy laugh of that creature, ruining an otherwise perfect moment._

_Light gently reminded her to study and not to forget to ask mom about those apples, before making his way up the stairs, the laughing creature in tow._

_Even though they left on a high note, she couldn’t help but feel uneasy about the whole interaction, and that’s ignoring the hallucination she just experienced. Sayu was sure he knew that their mother wouldn’t go overboard with buying apples of all things… If she didn’t just find out she was clinically insane, she would have thought her brother was trying to hide something._

_Before her mind could wander onto unsettling conclusions, the show she’d been waiting for had started._

_She spent the next hour with her brain tuning out any thoughts that weren’t about Hideki Ryuga, the unfamiliar taste of the consomme chips on her tongue._

* * *

- _Present day_ -

**...The television flickered to a new scene; A man’s voice opened the advert. “Amy wasn’t like other girls…” A young American actress appeared on screen. “I’m not like other girls.” Amy supplied.**

**“She could see spirits!” The announcer added. “Woah! You’re, like, totally a ghost!” Amy said to a man in a costume. “Follow Amy and her friends on their fun and fantastical adventure in the new series:** **_Amy the Spirit Slasher_ ** **!”**

Sayu scrunched her face at the trailer on screen. If anyone had asked her a month ago if she would like to see creatures that others couldn’t, her answer would’ve been a resounding ‘Yeah, that sounds cool!’. But now that she actually does… It’s not as fun and fantastical as that announcer made it out to be. This wasn’t going to be the start of some new adventure for her to go on, unless you count the eventual trip to the psych ward. Poor Amy doesn’t deserve such a cruel fate.

She didn’t really feel like watching any more T.V., but she also didn’t really want to get up either. So she stretched as far as she could to reach the remote, however in her attempt to be lazy, she fell onto the floor. “Ouch!” --At least she could turn the T.V. off. It’s a good thing nobody was in the room to see this, either.

Feeling a little pathetic, she rolled over to look up at the ceiling. The late afternoon sunlight streamed through the window onto her face. She watched the dust float around the room. The longer she watched them fading in and out of the sunlight, the more she noticed patterns they followed. The ones closer to her seemed more stagnant, and only moved when she breathed. The ones further from her drifted from right to left. Her eyes followed the flow to the air conditioning vent above. She’s never really noticed that there before, or if she did, never gave it much thought. Sayu pondered what else she hasn’t been noticing in her life. 

_“...How are you and Light even related, let alone the same species?”_ The words of that demon had nestled themselves into the side of her brain, like a thorn jammed through the sole of a thin shoe.

...What was she even doing with herself? She couldn’t just avoid the issue by contemplating the movement of dust in her house. There’s something happening to her. Something weird. And in all the classes, ‘Talk’-s and textbooks she’s had on puberty and adolescence, none of them mentioned seeing things. What could she even do about this? Tell her parents? Like, _“Hey, Mom, Dad, I’ve been seeing a demon following Light around!”?_ As if! That would only serve to demote her status from ‘mediocre second child’ to ‘the family nut-job’. 

Which… Isn’t much of a demotion, to be honest. 

She slapped her hands on her cheeks. _No, Idiot, pull yourself together. This is no time to feel sorry for yourself..._

With newfound determination, she trotted up to her room. She sat at her desk, and from her drawer pulled out a blank notebook and a pen.

At the top of the first page, she wrote in big, bold letters:

**WHAT IS WRONG WITH SAYU YAGAMI?**

She nodded, and closed the book and placed it in her school bag. Right now, she had to study. But tomorrow, she needed to stop by the library. There’s research to be done.


	2. I am Just A Girl

**Summary for the Chapter:**

> Sayu and her friends :)

“Light, you coming?” Sayu knocked on his door. The winter morning was particularly chilly. She had considered wearing her heaviest jacket, but it clashed with her school uniform. It has been decreed by the fashion gods themselves that the jacket was to be worn on weekends and holidays _only_. She settled on a neutral brown puffy sweater instead. It was not only comfortable, but cute. 

It felt nice to wear cute things. After all, who knows when some dashing young man will transfer to your school, take one look at you and think _“Wow, she’s so pretty in that puffy brown sweater, she has to be the one for me”_ ? And one day, after months of awkward tension and lighthearted banter between the both of you, he tells you to meet him behind the school after class, _and he holds up a rose and says--!_

“...Sayu, are you even listening to me?”

She focused her gaze and met familiar brown eyes, filled with confusion. “Hello? We can’t have you falling asleep again, we have to go to school.” Her brother gently knocked her on the head. Sayu mock-scowled at him. “Hey! I heard you, all right. I just didn’t wanna hear my brother’s dumb voice so early in the morning.” She stuck out her tongue, earning her a laugh. 

“All right, all right. Sorry for having a dumb voice, but we still have to go to school. Come on, mom’s probably waiting for us downstairs.” With that, the two siblings went downstairs together.

As Sayu sat to eat her buttered toast, she saw the demon ascend down through the ceiling, looking a little bored. A few weeks ago, she’d noticed that it wasn’t that talkative in the mornings. Watching it float around aimlessly in and out of her vision, she almost felt bad for the thing. Even if it was creepy and annoying, it wasn’t as if it caused trouble or anything. In fact, a few times some of the stuff it said was a little helpful. 

She thought back to last weekend, when she was stuck translating a paragraph for her english homework. The demon had floated into her room, complaining about not having anything to do. He then loomed behind her, and not only read the whole page for her aloud in perfect japanese, but even commented jovially that the original english paragraph wasn’t even grammatically correct. Pointing that out to the teacher the next day earned her some serious top marks.

After they finished eating, their mother walked them to the front door. 

“Sayu, Light, have a nice day today, okay?” She beamed at her children. “Oh, and by the way,” She pulled out a piece of paper from her apron pocket. “I found this in the mail this morning!” 

Sayu and Light looked at it together. It was a coupon for the local grocery store, with various vegetables and meats being listed as half-off from 3:30-6:00pm. It looked like the ingredients for a hot-pot. Sachiko Yagami smirked. “Can you guess what we’re having tonight?” Her eyes wandered over to Light, who gave her the answer. 

“Could it be… Hot-pot?” He raised his brow, inquisitively. Their mother laughed. “Bingo! You got it!” She pinched his cheek. “As expected of our resident detective-in-progress.” Light groaned and faintly swatted her hand away. “Mom…” 

“Wow, Light, you’re a real momma’s boy, aren’t ya? Heheh.” The gravelly voice next to Sayu mirthfully commented. That was another one of it’s weird habits, a lot of the time it tended to talk directly to her _brother_ , rather than to her. Which made no sense, since it was a construct of _her_ mind. She would tuck that piece of information away for after school.

“Now, since I’ll be going to the store, did you want me to get anything in particular?” Their mother asked. After hearing that, the demon looked to Light with pleading eyes. For a second, her brother almost looked… annoyed? Maybe he thought she was going to spill the beans to mom about his little obsession. Well, whatever emotion that was, it was quickly replaced by his own pleading look to Sayu.

She smiled at him knowingly. “Yeah, mom, could you pick up some more--“ Sachiko sighed. “Yes, yes, I know. Your apples, right? I didn’t forget about that… Listen, I’m glad you’re eating healthy, Sayu, but a new batch every week is a little much. You’re going to ruin your appetite.” She shook her head. “I’ll still get them for you, of course, but this time not as many, okay?” Sayu didn’t miss the slight disapproval in her voice, but she did ignore it.

Out of the corner of her eye, she saw the creature literally jump for joy. “Oh, What a reliable kid she is!” It said gleefully. “You know, I think I like her better than you, Light.” She couldn’t stop the small feeling of pride she got from hearing that. 

They all said their goodbyes to each other, and the two students set off for school.

Their walk was comfortably quiet. Light was reading some book on criminology, probably just to look cool or something. The demon was flying behind the two, humming the ending theme song of _Loving Dreamers ~La Petit Ensemble~_. Which, to be fair, was really catchy. It was like this all the way until they reached the gate to her school.

“See you later, Sayu.” Light made a simple wave-like gesture at her. 

“Have fun at school, kid!” The demon flailed his hands around oafishly. He was being awfully nice to her, maybe because of the apples? 

Either way, she waved and called back out to her brother. “Thanks for walking with me this morning, bro! Also, I’m gonna go study at the library after school, I’ll be home by dinner!”

She didn’t bother to look at his reaction, so she just made her way onto campus.

* * *

“Psst, Sayu!”

Sayu grinned. She knew that voice anywhere. “What’s up, Emi?” 

Her four-eyed companion adjusted her glasses. “Tsk, tsk, tsk! Oh, Sayu, don’t you know? I go by _Amy_ now!” 

“Yeah, that’s what I just said, Emi.” 

“ _Non_ , Sayu! It’s Amy! _A~m~y~!_ ” Her friend drew out the name in a sing-song manner.

“Hmm? I see.” Sayu hummed in thought, grabbing lunch from her bag. “So what prompted the sudden name change, then?” 

Her friend stared at her like she’d just said the sky was green. “You mean you _didn’t_ see the trailer for that awesome new show? The one that aired _right after_ _Loving Dreamers_ ~ _La petit ensemble~_ Which-- don’t lie to me, I know you saw it!” 

“Um… that weird American one about ghosts or something?” 

“That’s the one!!!” She could see her eyes sparkling behind those glasses.

Emi-- _er_ _Amy_ was a little eccentric. Sort of a geek, but she’s a good friend. They could talk for hours about absolutely nothing, and still have fun. 

“Could you imagine living like that, though?” Amy clenched her fist, in a way she probably thought might look cool. “Seeing the supernatural, and fighting against the evils of the world?”

Sayu nodded absently, taking a bite of rice from her lunch box… _Oh? Mom used the furikake flakes today._

Amy pouted. “Hey, why is your lunch more important than me? Are you really my best friend?” She put a hand to her chest, as if she were wounded. “I can’t believe I befriended such a cold-hearted woman.”

Sayu rolled her eyes, sighing in defeat. She grabbed a sausage from her lunch box, and held it out to Amy. “Here, if I give you this, will you forgive me?” 

“Apology accepted, thank you for the meal~!” She gratefully gobbled up the peace offering.

“In any case,” Amy said. “You didn’t answer my question!” 

Sayu finished off the rest of her lunch. “Well, I wouldn’t want to see spirits.” Before Amy could protest, she continued. “I mean, if someone told you they could see things you can’t, would you even believe them?” She put her lunchbox down onto her desk. “If you were the one to see strange things nobody else could see, would you even believe yourself?” 

Amy looked hard at her friend. “Sayu… you…”

“Oh, my bad.” Sayu laughed awkwardly. “That was weird, wasn’t it?” She quickly put her lunchbox away. _Man, I’ve really gotta pull myself together._ Amy kept on staring. “Sayu, that was…” She grasped Sayu’s hands. “Incredible! Wow, I didn’t know you could analyze television that well! Maybe I should invite you to the _Spirit Slasher_ web forums…” 

“What? Oh, um… Thanks but no thanks, Amy. I don’t think I have the time to start a new series.” For once in her life, she was almost grateful for the upcoming tests she has to study for. 

“Ugh… I get you.” Amy grimaced at the thought. “Hey, can I come over to your place this week?”

Sayu smirked. “So you can admire Light?”

Amy made a disgusted face. “Ew, what? No. So we can study.”

“You’ve seriously got to be the only one in this school who doesn’t have a crush on him.” She was right, too. All throughout her childhood, Sayu had many classmates who only befriended her to get closer to Light.

Amy sniffed in disapproval. “I’m not interested in _real boys_. They’re all disappointing. I’d take watching Hideki Ryuga on screen over seeing Light in the flesh any day.” They both took a moment to sigh longingly about the actor. 

They spent the rest of the lunch period discussing T.V. shows and catching up on the latest celebrity gossip. When the bell rang, Amy bid farewell, and left to go to her classroom. 

The rest of the day trudged slowly into the afternoon, finally reaching the end of school. Sayu said goodbye to Amy, and made her way to the library.

* * *

  
Well, the library was a bust. Sayu hung her head in her hands. No matter how much she looked, she could only ever find huge psychology textbooks full of words she couldn’t even begin to read. It would take days to decipher every single one. 

She leaned back in the library’s chair, glaring at the large pile of useless books she now had on the table. All that motivation she had yesterday was gone, leaving a testament to her own illiteracy in its wake. Grumbling, Sayu then began the strenuous process of putting these books away. It’s been a whole half hour and she’s got nothing done. Heck, she could have finished her homework by now. What a waste of time. She packed up her stuff into her bag, and slung it over her shoulder.

Using all her upper-body strength, she hauled the books to the nearest cart. If she remembered from the last time she was here… _There you are._ She rounded the corner to spy a single, rusty return cart. With a soft thud, she rid herself of the burden. 

“Oh, what a shame, those books will be sitting there for a while…” A raspy, unfamiliar voice hummed from somewhere. 

Sayu whirled around. There was nobody in the aisle with her. “Wh- Whose there?” She all but whispered.

Silence, followed by a contemplative noise… Where was that sound coming from?

“Child can you…? No, surely a mere coincidence.” The words floated through the air like dust.

_Like dust?_ _From above!_ Sayu shot her eyes up to the top of the bookshelves. Where she laid eyes upon… 

Perched above her like a gargoyle, was a humanoid figure. On its head was a cow’s skull, with horns like she’s never seen before. She couldn’t tell if it was a mask or not. It was wearing clothes made of some kind of fur, and from what she could see of its body, limbs that were long and skeletal, covered in paper-like flesh. It was hard to decipher, but looking at its eyes made her believe it to be just as surprised about this sighting as her.

“...Er. Hello? Can you really see me?” It asked, sheepishly. 

“Y-yes? Am I not supposed to?” Sayu managed to stammer out.

The thing shook its head. “No, humans shouldn’t be able to see us. Not without…” It gasped slightly, and patted down the side of its hip. Apparently finding nothing amiss, it sighed. Immediately it turned back to look at her, head tilted to the side. “How odd. I’ve never met a human like you.”

Sayu’s mind raced. ‘Us’? ‘Humans’? And an object that allows humans to see them? She had so many questions. 

“So… If you’re not human, then can I ask what you are?” 

It huffed. “How rude. I’m not a ‘what’, you know.” 

She snorted. “Okay, sorry, that wasn’t nice. Who are you?” 

The creature nodded in approval. “It’s fine, kid. The name’s Gook. I’m a shinigami!”

“A god of death? Woah, that’s crazy!” Sayu exclaimed. Gook cringed, and she heard a distant shushing from a disgruntled student. _Right, we’re still in a library._ “Sorry… That’s a really cool title.” 

The shinigami scratched its head bashfully. “You think so? I never gave much thought about it, but I guess you’re right.” It pushed itself down from the bookshelf. Now that he(?) was standing before her, he was a lot taller than she’d thought, even while hunched over. “Hey, so, um... I haven’t talked to anybody other than the piles o’ dust back home in a long time and…” Gook trailed off, but he pointed to a little bench in the corner. 

Sayu couldn't help but smile. This was just so _weird_. “Great, cause I’ve got lots of questions for you, Mr. Gook.” 

**Notes for the Chapter:**

> Sorry, it's a small slice of life chapter today. Gotta enjoy that normalcy before... well, y'know. Thanks again for reading! See you guys next chapter!


End file.
